Isolation is important for various reasons. For example, isolation is important where common mode noise may be a problem. Isolation is also important where high-speed data transmission may be subject to interference due to magnetic fields, and the like. Additionally, isolation is important where the ground of two devices are not compatible. Further, isolation can be important to protect patients in medical applications. These are just a few examples, which are not meant to be limiting.
Various devices have been developed for providing isolation. For example, an optical isolator (also known as an opto-isolator, optocoupler, photocoupler, or photoMOS) is a device that uses a relatively short optical transmission path to transfer a signal between elements of one or more circuit, typically a transmitter and a receiver, while keeping them electrically isolated. However, a disadvantage of optical isolators is that they can not typically operate at high speeds often desired in digital communications. Additionally, since optical isolators require an optical transmitting element and an optical detecting element, the size, cost and power consumption of such devices is often greater than desired.
To overcome many of the deficiencies of optical isolators, digital isolators have been developed. Some digital isolators are capacitively coupled. However, such devices are often larger than desired and/or are not compatible with integrated circuit fabrication techniques. Other digital isolator devices combine high speed CMOS and air-core or magnetic-core transformer technology to support high data speeds and low power. However, such transformers typically rely on windings that often cause the size and cost of the transformers to be greater than desired.